[TheForge] Christmas Projects?

[Doug Ayen]

Thus Spake xlch58 at swbell.net (xlch58 at swbell.net):
> Death, Politics and aches and pains without nary a mention of 
> blacksmithing.  Whats the average age on theForge these days 80  
> ;')       Anyway, I usually ask this every year since my son and I forge 
> gifts for friends.    What are all of you making for christmas gifts?    
> I have gotten in the habit of forging a number of sets of steak turners 
> and skewers to keep on hand for the odd guest old friend that shows 
> up.   I have also made a set of  walkway lites that are a small one foot 
> tall shepard hook supporting a small pan suspended from it.  A small 
> candle is placed on it.   They seem popular and are simple to make.  
> What are you guys making?
> 
> Charles
> 

Making single-piece forged paring/utility knives. 

The steel is d2, 3/8" stock that I bought a few years ago to fool around 
with. It has enough chromium to be semi-stainless, but enough other stuff
that it holds a good edge. 

I forged in the blades and widened the butts for the handle, and did a bit
of forging to get a shape I liked, leaving a bit unforged to act as an 
integral bolster.

The rough forged knives were all successfully profiled, beveled, and 
smoothed, using a 36 grit belt to do the profiling and beveling, and 
A100 (about 200 grit) for the smoothing. While I forged out 10, one 
seems to have run away, probably lurking under some equipment in the 
workshop somewhere. Final grinding before heat treat was A30, about 
1000 grit. I used a new Trizact "gator" A100 belt from 3M -- it's a 
structured abrasive, but instead of the pyramids, it has a different 
pattern, diagonal lozenges about 2mm wide by half a centimeter long. It 
seems to leave a better scratch pattern than the older style, and is 
supposedly waterproof and less likely to split. So far, can't argue -- 
I cool my blades in a quench bucket while grinding, and it was always a 
pain to have to dry off the knife completely when using the old style -- 
and if you didn't, even a drop was enough to mess up a belt -- the 
abrasive would turn into a paste, and clog up the belt.

Structured abrasives (Trizact from 3M, Norax from Norton Abrasives) are 
definitely the way to go. You can go straight from a 36 grit ceramic 
(non-structured) to the 100 micron structured abrasives with no problem, 
and without having to spend too much time cleaning up the 36 grit grind 
marks. I usually go for a mirror polish at 36 ceramic, structured A100, 
structured A36, then A16 and A6, and if I really want it to shine buff 
with pink rouge on a soft cotton buff.

These knives, however, are going to be a brushed finish. After some 
experimentation, I decided to go straight from the 220 grit to heat 
treat, then clean and finish up with a medium Scotchbrite belt.

But first I had to heat treat. Deciding to do things the "right way," I 
carefully assembled a package of the blades and a thermocouple in a 
stainless steel foil envelope, with a sacrificial carbon source (old oily 
rag) in to keep a reducing atmosphere. Into a stone cold heat treat oven, 
heat to 1,800 - 1,875 degrees F for 20 minutes. Or, as the case turned 
out, burn out your thermocouple somehow about halfway through and break 
out the spare and use that to determine the envelope temperature, then 
add in an extra 20 minutes to ensure thorough heat soaking and so get 
full hardness. A file test showed that the blades were at least harder 
than the file -- it skated right off of all of the blades without 
leaving a mark.

A quick air-quench later, and off to the cooler, where the quench is 
finished with liquid nitrogen. I put a couple of supports on the bottom 
of the cooler to keep the blade off the liquid nitrogen, poured in a 
half-inch, and gave it half an hour to get the blades down to cryogenic 
levels, adding in lN2 as needed. Once I was sure the blades wouldn't be 
shocked into pieces, I submerged them in the lN2 and let them sit for an 
hour.

Done with the cryo-quench, off to the heat treat oven. D2, the steel I 
used for these, has 2 maximum toughness/hardness peaks, the best one at 
450 deg, about RC59-60, so that's what I tempered these at (2 tempering 
cycles, one hour each.)

Once the blades cooled down for the 2nd time to room temperature, I tried a 
couple of different Scotchbrite belts, decided that while the coarse 
worked faster, the medium definitely had a better look to it. Somehow got 
some grease in the belt, though -- I'm going to try to get that out without 
damaging the belt somehow.

Having determined the finish, I did a round of sharpening. This is the 
preliminary sharpening -- while it gives a good, sharp edge, there are 
enough operations between now and the final product that I'll need to do 
one last sharpening before sending out the blades. I decided, since I 
had a few liters of liquid nitrogen around, to try something I've seen 
done with dry ice -- chill down the blade before grinding the edge in 
on the belt grinder. The theory is that with the blade at a chilly -321 F, 
to exceed the tempering temperature of 450F requires some 771 degree 
temperature rise. In practice, it seems to work -- using an A6 (2000+ 
grit) belt on slow speed usually requires a bit more care than I 
exercised, yet didn't distemper any blades, even on the tips (the 
hardest part to avoid distempering.) Still, at $3/liter, I'll be using 
dry ice next time, it's a lot cheaper.

So, the blades are all sharpened, but need a cleanup, the brushed finish 
put on, and then I should be done. 

--doug
Blackanvil Forge

blacksmithing journal at:
blackanvil.livejournal.com